Frustum implementation

frustum.h

#ifndef FRUSTUM_H
#define FRUSTUM_H

#include "vector.h"

class Frustum {
 
public:

 void initialize(float angle, float ratio, float nearDistance);
 void destroy();
 
 void update(VECTOR3D position);

 VECTOR3D up;
 VECTOR3D right;
 VECTOR3D orientation;
 
 VECTOR3D nearCenter;
 VECTOR3D nearTopLeft;
 VECTOR3D nearTopRight;
 VECTOR3D nearBottomLeft;
 VECTOR3D nearBottomRight;

 float modelview[4*4];
 
 float view[3];
 float position[3];
 
 float nearDistance;
 
 float nearHeight;
 float nearWidth;

private:

};

#endif

frustum.cpp

#include <gl.h>
#include <math.h>
#include "mymath.h"
#include "frustum.h"

void Frustum::initialize(float angle, float ratio, float nearDistance) {
 
  // Register parameters
  this->nearDistance = nearDistance;
 
  // Compute the width and height of the near and far plane sections
  float tang = (float) tan((PI / 180.0f) * angle);
 
  nearHeight = nearDistance * tang;
  nearWidth = nearHeight * ratio; 
}

void Frustum::destroy() {
}

void Frustum::update(VECTOR3D position) {
 
  // Calculate up- and right-vector
  glGetFloatv(GL_MODELVIEW_MATRIX, modelview);
 
  up.x = modelview[1];
  up.y = modelview[5];
  up.z = modelview[9];
 
  right.x = modelview[0];
  right.y = modelview[4];
  right.z = modelview[8];
 
  orientation.crossProduct(up,right);
 
  // Normalize vectors
  up.normalize();
  right.normalize();
  orientation.normalize();
 
  // Calculate center of near frustum
  nearCenter = (orientation * nearDistance * 1.2f);
 
  // Calculate corners of near frustum
  nearTopLeft     = nearCenter + (up * (nearHeight / 2.0f)) - (right * (nearWidth / 2.0f));
  nearTopRight    = nearCenter + (up * (nearHeight / 2.0f)) + (right * (nearWidth / 2.0f));
  nearBottomLeft  = nearCenter - (up * (nearHeight / 2.0f)) - (right * (nearWidth / 2.0f));
  nearBottomRight = nearCenter - (up * (nearHeight / 2.0f)) + (right * (nearWidth / 2.0f));
 
  // Calculate view vector
  view[0] = nearCenter.x;
  view[1] = nearCenter.y;
  view[2] = nearCenter.z;
 
  // Calculate position vector
  Frustum::position[0] = position.x;
  Frustum::position[1] = position.y;
  Frustum::position[2] = position.z;
}